holes in 3mm steel. Biggish ones, around 12mm dia. What bits do you recommend? Anything from our hosts? Thanks.
You do not say exactly how many holes, just lots? Normally in thick steel (plates, RSJ's etc) you would use a Rotabroach machine, they are mag mounted drills with special bits and very easy to use. Because of the electric mag mount they can be used upside down or easily slid around plate steel and at least you won't spin around the drill when it snaggs. Just google rotabroach hire here is an example http://thetoolhireshop.com/product/magnetic-stand-and-rotabroach-drill/
hole saw and a de-burring tool, SF do the Bosch ones which are fairly reasonable if the work-piece isnt overly large, and has 100s of holes, find someone with a laser or water jet, find the right place and they'll have it done in no time, no burrs to clean up and very cheap
isn't a RB just a little bit of overkill for 3mm thickness ? - if it's just normal Chinese mild steel you don't need anything so powerful
Yes I agree too Sean, should have clarified for lots of holes only. Hole cutter as you suggest, stepped cutter, 12mm HSS bit can just do a few.
I would tend to use a decent HSS twist drill...The DeWalt or Bosch should be fine with a decent cutting lube such as Dormer Supercut or Rocol RTD. I would normally drill a pilot hole first when drilling 12mm , using a centre drill or a 4mm or similar twist drill.
Using a hole saw for 12mm WTF, If you have a big stand drill you could probably do it in one go with a jobber or else 4, 8 then 12 or 6 then 12.
Chust wondering if there was a recommended brand or type. I've used standard jobbers from our hosts, and tbh they were a bit pants - lost their edge very quickly.